A systematic review of the cell death mechanisms in retinal pigment epithelium cells and photoreceptors after subretinal hemorrhage - Implications for treatment options.

Humans rely on vision as their most important sense. This is accomplished by photoreceptors (PRs) in the retina that detect light but cannot function without the support and maintenance of the retinal pigment epithelium (RPE). In subretinal hemorrhage (SRH), blood accumulates between the neurosensory retina and the RPE or between the RPE and the choroid. Blood breakdown products subsequently damage PRs and the RPE and lead to poor vision and blindness. Hence, there is a high need for options to preserve the retina and visual functions. We conducted a systematic review of the literature in accordance with the PRISMA guidelines to identify the cell death mechanisms in RPE and PRs after SRH to deepen our understanding of the pathways involved. After screening 736 publications published until November 8, 2022, we identified 19 records that assessed cell death in PRs and/or RPE in experimental models of SRH. Among the different cell death mechanisms, apoptosis was the most widely investigated mechanism (11 records), followed by ferroptosis (4), whereas necroptosis, pyroptosis, and lysosome-dependent cell death were only assessed in one study each. We discuss different therapeutic options that were assessed in these studies, including the removal of the hematoma/iron chelation, cytoprotection, anti-inflammatory agents, and antioxidants. Further systematic investigations will be necessary to determine the exact cell death mechanisms after SRH with respect to different blood breakdown components, cell types, and time courses. This will form the basis for the development of novel treatment options for SRH.

The potential of marine resources for retinal diseases: a systematic review of the molecular mechanisms.

We rely on vision more than on any other sense to obtain information about our environment. Hence, the loss or even impairment of vision profoundly affects our quality of life. Diet or food components have already demonstrated beneficial effects on the development of retinal diseases. Recently, there has been a growing interest in resources from marine animals and plants for the prevention of retinal diseases through nutrition. Especially fish intake and omega-3 fatty acids have already led to promising results, including associations with a reduced incidence of retinal diseases. However, the underlying molecular mechanisms are insufficiently explained. The aim of this review was to summarize the known mechanistic effects of marine resources on the pathophysiological processes in retinal diseases. We performed a systematic literature review following the PRISMA guidelines and identified 107 studies investigating marine resources in the context of retinal diseases. Of these, 46 studies described the underlying mechanisms including anti-inflammatory, antioxidant, antiangiogenic/vasoprotective, cytoprotective, metabolic, and retinal function effects, which we critically summarize. We further discuss perspectives on the use of marine resources for human nutrition to prevent retinal diseases with a particular focus on regulatory aspects, health claims, safety, and bioavailability.

[Effect of Selective Retina Therapy (SRT) on the Inflammatory Microenvironment of the Subretinal Space]. / Einfluss der Selektiven Retinatherapie (SRT) auf inflammatorische Zellmediatoren des subretinalen Raums.

PURPOSE: To investigate the effect of Selective Retina Therapy (SRT) on inflammatory key factors such as complement factor-C3 (CC3), tumor growth factor-beta2 (TGF-ß2), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ). MATERIALS AND METHODS: Porcine RPE-Bruch's membrane-choroid explants were irradiated with two SRT laser systems, SRTYLF and SRTYAG (Nd : YLF laser, wave length 527 nm, pulse duration 1.7 µs and Nd : YAG laser, wave length 532 nm, pulse duration 2.4 - 3 µs). Laser irradiation was performed on a spot size of 200 × 200 µm, 30 pulses, with a repetition rate of 100 Hz, and a radiant exposure of 140 (threshold RPE death) and 180 mJ/cm2 per pulse (above threshold RPE death). Explants were cultivated in modified Ussing chambers and culture viability was assessed by calcein-AM cell staining. Secretion of inflammatory factors was analyzed by ELISA. Protein expression of tissue explants was assessed by Western blot. RESULTS: Regeneration of RPE was observed after 4 days. One day after SRT with 140 mJ/cm2 per pulse the secretion of basal CC3 decreased in ELISA. Following 180 mJ/cm2 radiant exposure, the level of IFN-γ decreased at day 4. CONCLUSION: SRT does not induce the release of the pro-inflammatory factors analyzed in this in-vitro study.

Nicotine reduces VEGF-secretion and phagocytotic activity in porcine RPE.

BACKGROUND/PURPOSE: Smoking is a strong environmental factor for the development of age-related macula degeneration. In this study, we investigated the effects of nicotine on RPE cell function in porcine in vitro models, focussing on cell death, VEGF secretion and phagocytotic ability. METHODS: For these experiments, perfusion organ culture and primary RPE cell culture were used and exposed to nicotine up to 7 days. Survival was investigated in primary porcine RPE cells in an MTT and trypan blue exclusion assay. VEGF secretion was investigated in a porcine perfusion organ culture model using ELISA. A phagocytosis assay using FITC-labelled latex beads in primary RPE cells was used to assess the phagocytotic ability of the cells. RESULTS: Nicotine does not induce cell death in the RPE at any time point up to 7 days of stimulation at any tested concentration. VEGF secretion, however, is diminished compared to untreated control already after 1 day of nicotine treatment and even more profoundly up to 7 days. Furthermore, phagocytotic ability of the RPE is diminished by nicotine in the highest concentrations tested (100 µM). CONCLUSION: Nicotine impedes RPE function (VEGF secretion, phagocytosis), which could be directly involved in the development of dry AMD and geographic atrophy.

Different properties of VEGF-antagonists: Bevacizumab but not Ranibizumab accumulates in RPE cells.

BACKGROUND: Vascular endothelial growth factor (VEGF) antagonists are currently the therapy of choice for age-related macular degeneration. Here we compared the effects of FDA-approved Ranibizumab and off-label used Bevacizumab on RPE cells, investigating their respective uptake by RPE cells over time. METHODS: Primary porcine RPE cells were treated with Bevacizumab or Ranibizumab, respectively. Uptake of the respective VEGF-antagonists was assessed with confocal laser scanning microscopy and flow cytometry. Cell death was assessed with MTT assay and VEGF secretion was measured with ELISA. RESULTS: When clinical doses were applied for 1 h, Bevacizumab was taken up by RPE cells as assessed by confocal laser scanning microscopy and flow cytometry. After 24 h of incubation, and further assessed after 1d, 5d, and 7d, Bevacizumab was detected in RPE cells where it accumulated over time. The presence of Bevacizumab within RPE cells after 7d was confirmed by flow cytometry. While some Ranibizumab was found in RPE cells after 1 h of incubation when assessed with confocal laser microscopy but not by flow cytometry, no signal above control was detected after 1d, 5d, or 7d. Neither substance induced significant cell death after 7 days and no inhibitory effect on VEGF secretion was observed after day 3 of culture. CONCLUSIONS: Bevacizumab, but not Ranibizumab, accumulates in RPE cells over time, implying substantial differences between these two drugs.